Improve explanation of asymmetric visibility (#3989)

Author: mmalferov

appendices/migration84/new-features.xml

@@ -62,14 +62,17 @@ print $p->fullName; // Prints "Peter Peterson"
    <title>Asymmetric Property Visibility</title>
 
    <simpara>
-    Object properties may now have their <literal>set</literal> visibility controlled separately from the <literal>get</literal> visibility.
+    Object properties may now have their <literal>set</literal> visibility
+    controlled separately from the <literal>get</literal> visibility.
    </simpara>
    <informalexample>
     <programlisting role="php">
 <![CDATA[
 <?php
 class Example
 {
+    // The first visibility modifier controls the get-visibility, and the second modifier
+    // controls the set-visibility. The get-visibility must not be narrower than set-visibility.
     public protected(set) string $name;
 
     public function __construct(string $name)